JP2004074151A - Plastic material identification apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material identification apparatus capable of sorting and recovering specified plastics from recycled wastes discharged from homes and waste plastics discharged as industrial wastes. <P>SOLUTION: A material identification apparatus has a pretreatment and sorting device (21) substantially classifying plastics, a belt conveyor (26a, 26b) aligning and carrying the pretreated plastics, a light source (31) irradiating with near-infrared rays to the plastics, a photodetector (32) detecting transmission light or reflected light from the plastics which are irradiated by the light source (31) and is characterized by being provided with an identification device (29) identifying materials by absorbance of a particular wavelength from the plastics and a sorting device (30) controlled by the identification device (29). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plastic material identification device, and more particularly to a plastic material identification device applied to the separation and collection of specific plastics from resource waste discharged from homes and waste plastics that are industrial waste.
[0002]
[Prior art]
Conventionally, regarding the separation of waste plastics, it has been known to separate plastics using a specific gravity difference of plastics using a hydrocyclone. Specifically, polyethylene (specific gravity 0.93) and polystyrene (specific gravity 1.05) were obtained at a concentration of 98.6% for polyethylene lighter than the upper discharge and at a concentration of 94.7% for polystyrene heavier than the lower discharge. Have been. In addition, wind sorting and sinking sorting are also performed efficiently using the difference in specific gravity. FIG. 5 shows an example of a conventional waste plastic discriminating method.
[0003]
Waste plastic (raw material) 1 is first supplied to a crusher 2. The waste plastic 1 after crushing is sent to the storage tank 3 and is temporarily stored. After that, the waste plastic 1 is supplied to the stirring storage tank 5 from the quantitative supply device 4 arranged on the lower side of the storage tank 3. A constant amount of water 6 is supplied to the stirring storage tank 5 and adjusted to a constant concentration. Next, the mixture of the plastic and water is quantitatively supplied to the liquid cyclone 8 by the centrifugal pump 7 whose rotation speed is controlled, and the low-specific-gravity plastic is discharged from the upper part of the cyclone to the washing and dehydrating machine 9, and the water and the plastic are discharged. The low specific gravity plastic is stored in the low specific gravity storage 10 and the water is stored in the circulating water tank 11. The high-density plastic is discharged from the lower part of the liquid cyclone 8 together with the high-density plastic and water, and the water and the plastic are separated by the washing and dehydrating machine 12. . As a product, specific gravity plastics are taken out of the specific gravity storage 13 and small specific gravity plastics are taken out of the specific gravity storage 10.
[0004]
[Patent Document 1]
Japanese Patent Publication No. 06-506149 [Patent Document 2]
US Pat. No. 5,134,291 [Patent Document 3]
Japanese Patent Application Laid-Open No. 06-210632 [Patent Document 4]
JP-A-61-192380
[Problems to be solved by the invention]
However, according to the prior art, there are the following problems.
(1) Polyethylene (0.93) and polypropylene (0.90 to 0.91) having substantially the same specific gravity cannot be separated. Further, in the prior art, it was difficult to separate plastic having no (small) difference in specific gravity. Further, if not pulverized, the fluidity in the hydrocyclone is poor, and clogging occurs and separation cannot be performed.
[0006]
(2) When discriminating the material of waste plastics using a near-infrared identification device, it is very difficult to arrange the waste plastics by type without overlapping them one by one on a conveyor.
(3) When recycling waste plastic, it is necessary to separate the identified materials at high speed.
[0007]
The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a plastic material identification device capable of separating plastic having a small difference in specific gravity and separating plastic without crushing.
[0008]
[Means for Solving the Problems]
A first means of the present invention includes a pre-processing and sorting device for roughly separating plastic, a conveying device for aligning and conveying pre-processed plastic, a light source for irradiating near-infrared light to the plastic, and an irradiation light from the light source. Having a light receiving element for detecting transmitted light or reflected light from the plastic, an identification device for identifying a material by absorbance of a specific wavelength by the plastic, and a classification device controlled by the identification device. It is a plastic material identification device characterized by the following.
[0009]
In the present invention, the second means, when identifying by the identification device, the specific wavelength of the transmitted light or reflected light from the plastic, when polyethylene terephthalate (PET), one absorption peak appears in 1660 ~ 1669nm, One absorption peak appears at 1677 to 1698 nm for polystyrene (PS), two absorption peaks appear at 1710 to 1726 nm and 1726 to 1735 nm for polypropylene (PP), and 1716 for polyvinyl chloride (PVC). The type of plastic can be identified by two absorption peaks appearing at １７1729 nm and 1746-1754 nm, and in the case of polyethylene (PE), by one absorption peak appearing at 1710-1735 nm.
[0010]
A third means of the present invention is the plastic material identifying apparatus according to the first means or the second means, wherein the pretreatment sorting device has a plastic moving device and a pulse air nozzle.
[0011]
A fourth means of the present invention is characterized in that the pre-processing and sorting apparatus is configured to blow plastic by an air-selecting fan to move plastic on the vibrating screen conveyor, and sort the moved plastic by a pulse air nozzle. The plastic material identification apparatus according to the first to third means.
[0012]
The fifth means of the present invention is characterized in that the conveying device is constituted by a plurality of conveyors arranged in a co-current flow on the blowing side of the pulse air nozzle. Material identification device.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a plastic material identification apparatus according to an embodiment of the present invention will be described with reference to FIGS. Here, FIG. 1 is an explanatory diagram of a pre-processing selection device that is one configuration of the identification device, and FIG. 2 is an explanatory diagram of a near-infrared identification device and a classification device that is one configuration of the identification device.
[0014]
First, the pre-processing sorting device 21 will be described with reference to FIG. Reference numeral 22 in the figure denotes an air selection fan that disperses waste plastic (hereinafter abbreviated as waste plastic) sent from a raw material waste plastic hopper on a conveyor described later. The waste plastic that has passed through the vibrating screen conveyor 23 by the wind selection fan 22 is roughly classified by a plurality of pulse air nozzles 24 having a constant pressure. In other words, heavy waste plastics such as the bottle 25 are scattered only near (within 1 m) and reach the conveyor 26a, and light waste plastics such as the tray 27 are distant (1m or more) and reach the conveyor 26b. Further, small waste plastics, for example, those having a size of 30 mm × 30 mm or less (small items such as caps 28) are removed from the vibrating screen conveyor 23 because they are small in quantity. This improves the performance of the overall system (preprocessing, identification and sorting device) (improves accuracy and increases throughput). As described above, the pretreatment sorting device 21 mainly includes the wind selection fan 22, the vibrating screen conveyor 23, and the pulse air nozzle 24. The conveyors 26a and 26b are arranged in parallel on the side of the pulse air nozzle 24 blowing out, and function as a transport device.
[0015]
Next, the near-infrared identification device 29 and the classification device 30 will be described with reference to FIG. The near-infrared identification device 29 includes a halogen tungsten lamp (light source) 31 that emits near-infrared light, and a light receiving unit that includes PbS and InGaAs that detects transmitted light or reflected light of the irradiation light from the light source 31 from the waste plastic. It comprises an element 32 and a spectroscope 33 such as a filter arranged between the light source 31 and the light receiving element 32. Here, among the waste plastics, heavy ones such as bottles and light ones such as trays, vinyls and films were arranged on the belt conveyor 34, and then the materials were identified by absorbing near-infrared rays of a specific wavelength. An amplification circuit 35, a personal computer 36, and a static converter 37 are electrically connected to the light receiving element 32 in this order. An electromagnetic valve 39 provided on a header 38 is connected to the static converter 37.
[0016]
The separation device 30 has a separation box 40 having a plurality of rooms 40a to 40d. The waste plastic identified for each material is controlled by a solenoid valve 39 to control high-pressure air (for example, 6 kg / cm 2), and high-pressure air is discharged in a pulsed manner from a pulse air nozzle 41, so that the waste plastic is discharged to each of the chambers 40 a to 40 d of the separation box 40. Blown away. For example, a PET bottle is stored in the room 40a, a PVC bottle is stored in the room 40b, a PE bottle is stored in the room 40c, and other bottles such as detergent and mayonnaise are stored in the room 40d.
[0017]
As described above, the plastic material identification device according to the above-described embodiment is a pre-processing sorting device 21 configured to roughly separate plastic, including a wind selection fan 22, a vibrating screen conveyor 23, a pulse air nozzle 24, and the like. Conveyors 26a and 26b for aligning and conveying pretreated plastics, a light source 31 for irradiating the plastic with near-infrared rays, and a light receiving element for detecting transmitted light or reflected light from the plastic of irradiation light from the light source 31 32, and a sorting device 30 having a sorting box 40 that sorts and stores various plastics identified by the identifying device 29 with high-pressure air from the pulse air nozzle 41.
[0018]
The operation of the plastic material identification device having the above configuration is as follows. When identifying the material of the waste plastic using the near-infrared identification device, it is necessary to align the waste plastics one by one without overlapping each other, but it is very difficult to align the waste plastics. However, in the material identification apparatus of the present invention, the pre-processing and sorting apparatus 21 separates the cap 28 and the like from the waste plastic and mechanically pre-processes the bottles 25 and the trays 27 so that the near-infrared ray in the downstream can be obtained. The accuracy of the expression identification device 29 is improved.
[0019]
Specifically, of the 100 waste plastics, for example, 10 caps (small ones) were dropped from the vibrating screen conveyor 23 of 30 mm × 30 mm or less. Next, 50 heavy items (30 PET bottles and 20 other bottles) are dropped on the nearby conveyor 26a using the air selection fan 22 and the pulse air nozzle 24, and 40 light items (20 trays, Ten vinyls, ten films, etc.) were dropped on a distant conveyor 26b using a wind selection fan 22 and a pulse air nozzle 24. As a result, the waste plastic recovered from the conveyor 26a was 100% bottles. As described above, since the amount of light waste plastic (for example, cap 28) having a size of 30 mm × 30 mm or less is small, the performance of the entire system (pre-processing, identification and sorting apparatus) can be reduced by dropping and removing it from the vibrating screen. Improved (accuracy improved and throughput increased).
[0020]
In the near-infrared identification device 29, the aligned bottles are irradiated with near-infrared light by the light source 31 to the sample, and thereafter, the spectroscope 33 receives the light transmission amount of a wavelength unique to the sample to the light receiving element 32. The absorbance of each wavelength of each sample is calculated by the following equation (1) to identify the material.
[0021]
A = log (T1 / T2) (1)
Here, T1: the transmitted light amount of air when there is no sample T2: the transmitted light amount when there is a sample A: absorbance By the way, the infrared light is light having a wavelength of 2.5 μm to 16 μm, and this is irradiated with infrared light. At this time, when the vibration cycle of the infrared ray does not match the vibration cycle of a certain atom, the infrared ray does not affect the molecules of the plastics, but is merely transmitted as it is. However, if the periods match, each atom or atomic group absorbs its energy according to each period, and the vibration changes from the ground state to the excited state. And appears as absorption in the infrared spectrum.
[0022]
However, as shown in Japanese Patent Application No. 5-5042, if water adheres to the plastic, the accuracy decreases sharply. In general, by using near-infrared light having a short wavelength (0.8 to 2.5 μm, high frequency), the absorbance of water is weakened to maintain accuracy. However, as shown in FIG. 3, the absorption peaks appear to overlap from 1662 nm to 1748 nm, and high measurement accuracy and a sophisticated algorithm are required. The present invention, as an advanced discrimination, algorithm, is not to judge simply by the wavelength of the absorption peak alone, but to comprehensively judge the material using the number of absorption peaks and the ratio of the height of each absorption peak. .
[0023]
Next, the high-pressure air (6 Kg / cm ² ) downstream is controlled by the solenoid valve 39 in accordance with the identified signal, and the high-pressure air is ejected in a pulsed manner by the pulse air nozzle 41, and the sample is collected in each room of the sorting box 40. 40a to 40b. The material in each room was tested on a total of 100 samples, and each of PET, PVC, and PE was tested on 10 samples. The test was performed with 100% accuracy.
[0024]
【Example】
(Embodiment 1) Embodiment 1 is an example using a light receiving element made of PbS (lead sulfide). No. For five samples of Nos. 1 to 5, five types of materials of PP (No. 1), PE (No. 2), PVC (No. 3), PS (No. 4) and PET (No. 5) were determined. To this end, the sample was irradiated with near-infrared light at an incident angle of 45 degrees, and the reflected light was received by the light receiving element 32 at a reflection angle of 50 degrees. Based on the light amount R (sample reflected light amount) and the light amount R (mirror reflected light amount) when totally reflected by the mirror, the absorbance A was calculated by the following equation (2).
[0025]
A = logR (mirror reflected light amount) −logR (sample reflected light amount) (2)
Next, in order to determine the absorption peak wavelength, the absorbance A ′ (without unit) was calculated by the following equation (3).
[0026]
A ′ = (A−Amin) / (Amax−Amin) (3)
However, Amax: the maximum amount of absorbance within the integrated range Amin: the minimum amount of absorbance within the integrated range The result is shown in FIG. As shown in FIG. 3, the single absorption peak in the range of 1600 nm to 1800 nm No. 2, PE No. 2 4 PS, No. 4 5, the peaks of which are 1732 nm, 1682 nm and 1662 nm, respectively. The two absorption peaks are No. No. 1 PP, No. 1 No. 3 for PVC, which appears at 1710 nm and 1730 nm for PP, and at 1716 nm and 1748 nm for PVC. Therefore, from the number of peaks and the peak wavelength, No. 1 to No. Five types of plastic materials up to 5 could be judged 100%.
[0027]
(Embodiment 2) Embodiment 2 is an example using a light receiving element made of InGaAs (indium gallium arsenide). The same No. as in the first embodiment. 1 to No. The sample was irradiated with near-infrared light perpendicularly to the five kinds of five materials, and the transmitted light was received by the light receiving element 32. The absorbance A was calculated from the light amount T (sample) based on the transmitted light amount T (reference) of air by the following equation (4).
[0028]
A = logT (reference) −logT (sample) (4)
Next, to determine the absorption peak wavelength, the absorbance A ′ was calculated from the above equation (3). The result is shown in FIG. From FIG. Regarding 3, when the absorbance A is converted to the absorbance A ′ for the range of 1641 nm to 1763 nm, 1726 nm is 1.0, and when the absorbance A is converted to the absorbance A ′ for the range of 1735 nm to 1763 nm, 1735 nm becomes 1.0 and 0.0, and the difference between 1745 nm and 1754 nm was 0.05 or less, and it was determined that the material was PVC.
[0029]
No. Regarding 1, when the absorbance A was converted to an absorbance A ′ for the range from 1641 nm to 1763 nm, the absorbances A ′ at 1716 nm, 1726 nm, and 1735 nm became values of 0.88 or more, and it was determined that the material was PP. .
[0030]
No. Regarding 2, when the absorbance A was converted into the absorbance A 'in the range of 1641 nm to 1763 nm, 1735 nm became 1.0, and it was determined that the material was PE.
[0031]
No. Similarly, when the absorbance A was converted to the absorbance A 'for the range of 1641 nm to 1763 nm for 1, the value of 1688 nm became 1.0, and it could be determined that the material was PS.
[0032]
Finally, No. As for the sample No. 5, similarly, when the absorbance A was converted to the absorbance A ′ in the range of 1641 nm to 1763 nm, the value of 1669 nm became 1.0, and it was determined that the material was PET.
[0033]
The numerical value of the measurement wavelength jumps from 9 to 10 because near-infrared rays are irradiated at every wavelength of 9.4 nm, and is caused by rounding off to the first decimal place. As described above, according to the above embodiment, the following effects are obtained by determining the material of the waste plastic from the wavelength and number of the absorption peak in the absorbance spectrum of the present invention and the height of the peak.
[0034]
(1) There is almost no difference in specific gravity between polyethylene (specific gravity 0.93) and polypropylene (specific gravity 0.90), and they cannot be separated by a hydrocyclone or the like that is separated using the specific gravity difference. However, in the present invention, the polyethylene absorption peak is one peak from 1710 nm to 1735 nm, and the polypropylene absorption peak is two absorption peaks appearing from 1710 nm to 1726 nm and from 1726 nm to 1735 nm. Can be identified. After identification, the material placed on the conveyor can be blown off with high-pressure air or the like to separate the materials.
[0035]
(2) The difference in specific gravity between the PVC bottle (specific gravity 1.17 to 1.25 soft) and the PET bottle (specific gravity 1.38) is small, and it is difficult to separate PVC and PET based on the specific gravity difference. However, in the present invention, identification is possible as in the above (1).
[0036]
【The invention's effect】
As described above in detail, according to the present invention, as pretreatment of the identification device, i) small ones such as bottle caps, ii) light ones such as trays, vinyl and film, and iii) heavy ones such as bottles , The accuracy and the processing amount of the downstream identification device are improved. In addition, by cutting out the large classified samples on a conveyor and arranging the samples one by one without overlapping, the accuracy and the throughput of the identification device are improved.
[Brief description of the drawings]
FIG. 1 is an explanatory view of a pre-processing and sorting apparatus which is one configuration of a plastic material identifying apparatus according to one embodiment of the present invention.
FIG. 2 is an explanatory diagram of a near-infrared identification device and a separation device, which are one configuration of a plastic material identification device according to an embodiment of the present invention.
FIG. 3 is a characteristic diagram showing the relationship between the absorbance (reflection type) of plastic and wavelength.
FIG. 4 is a characteristic diagram showing the relationship between the absorbance (transmission type) of plastic and the wavelength.
FIG. 5 is an explanatory view of a conventional waste plastic discriminating method.
[Explanation of symbols]
Reference numeral 21: Pre-processing and sorting device 22: Wind selecting fan 23: Vibrating screen conveyor 24: Pulse air nozzle 29: Near infrared identification device 30: Sorting device 31: Light source 32: Light receiving element 33: Spectroscope 34: Conveyor belt 35 Amplification circuit 36 Personal computer 37 Static converter 38 Header 39 Solenoid valve 40 Sorting box 41 Pulse air nozzle

Claims (2)

A pre-processing sorting device for roughly separating plastic, a conveying device for aligning and conveying pre-treated plastic, a light source for irradiating the plastic with near-infrared light, and light transmitted from the plastic of irradiation light from the light source or A plastic material identification device comprising a light receiving element for detecting reflected light, an identification device for identifying a material by absorbance of a specific wavelength by the plastic, and a classification device controlled by the identification device. . At the time of identification by the identification device, the specific wavelength of the transmitted light or the reflected light from the plastic is one absorption peak appearing at 1660 to 1669 nm in the case of polyethylene terephthalate, and one absorption peak appearing at 1677 to 1698 nm in the case of polystyrene. By peaks, two absorption peaks appearing at 1710 to 1726 nm and 1726 to 1735 nm for polypropylene, two absorption peaks appearing at 1716 to 1729 nm and 1746 to 1754 nm for polyvinyl chloride, and 1710 to 1735 nm for polyethylene The plastic material identification apparatus according to claim 1, wherein the type of plastic is identified by one absorption peak appearing in (1).

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